In many commercial applications, bulk lengths of photosensitive web materials, such as photographic paper or film, are provided in roll form and mounted for rotation within light-tight convenience cassettes, commonly referred to as daylight load cassettes. The cassettes may include internal features for driving the web material from the cassette, such as shown in U.S. Pat. Nos. 3,722,999, 3,691,921, 4,928,897 and 5,362,008; or may simply dispense the web material to an external device which extracts the web material, such as shown in U.S. Pat. No. 5,187,531. Cassettes have also been used to remove lengths of exposed photographic film from an associated camera and wind the lengths onto a driven spool or scroll the lengths into a chamber, such as those shown in U.S. Pat. Nos. 1,764,450, 2,492,900 and 3,499,376. An exit slit through the wall of the housing typically includes some sort of static light lock, such as shown in U.S. Pat. No. 4,894,674; or a movable cover for opening and closing the exit slit. In some of the known apparatus, the movable cover also includes a sharpened edge for cutting the material.
In use, a cassette for dispensing web material is loaded into an associated apparatus, such as a "minilab" photographic printer, camera magazine loader or the like, to provide a supply of the material which can be dispensed or extracted from the cassette and cut into short lengths, upon demand. Such apparatus normally operates in a daylight environment and has external panels or cabinetry to prevent ingress of light. A chamber for receiving the cassettes is provided with some form of light-tight door or cover.
While daylight load cassettes of this general type have seen extensive commercial use, a problem can arise when an empty cassette must be replaced with a full one or when one cassette enclosing a partially used roll of a first type of web material must be replaced with another cassette enclosing a second type of web material. Typically, such cassettes have been delivered with a leading end of the web material or an added leader of other material extended from the cassette to be grasped by an operator and threaded into the associated apparatus or attached to a trailing end of a previously loaded web. The light-tight door or cover is then closed and the apparatus is operated to eject any web material that was exposed to light. And, if a first, partially emptied cassette is exchanged for a second one enclosing a different web material, an additional length of material from the first cassette must be exposed when the light-tight door is opened. Thus, a need has existed for a cassette which can be inserted into an associated apparatus, and removed from the apparatus while only partially emptied, without any portion of the enclosed web material extending beyond the light-tight interior of the cassette to be exposed while the light-tight door of the associated apparatus remains open.